When Sarah Jane Lytton came to England from Africa to go to the Harton School of Boys and Girls, she never dreamed that she would be learning not only math and spelling, but how to use her psychic powers as well. And she would also gain a friend, the street-girl Nan, whom she helped rescue from the brothel-men her own mother sold her to for money for liquor.
Sarah also gets back her African friend Grey, an African Gray parrot, and Nan gets Neville, a Raven from amongst those at the Tower of London. Those will be vital in saving them when the two of them are locked into a house with an evil elemental bound to it. But in the confusion, Nan discovers her own power as a Warrior of Light, the same as Memsab and Sahib Horton and their three friends. Sarah Jane earlier discovered her powers as a natural medium, putting her in danger from too many grieving quality wanting to contact their loved ones again and again.
But who could have wanted the two little girls dead? The Hartons and the girls won't be able to find out until the entire school goes to the countryside for the summer and Isabelle Harton encounters an old friend, David Alderscroft, now a rising young fire mage and called "The Wizard of London". David's mentor, Cordelia, is an air mage with enough of a touch of fire that she can mentor and tutor him.
But unknown by all, Cordelia has sold her soul to the creatures of Negative Fire, or Elemental Cold, and wants to take over David's body and life for her own. The only possible way to save him involves them all, not to mention a spirit of the Fey named Puck. Can they save David from himself and the twisted mentorship of Cordelia before it's too late?
I always enjoy Mercedes Lackey's books, and this time I feel she did a wonderful job in portraying the main character's powers, which had nothing to do with elementals, but rather psychical powers. I found the powers to be realisticly portrayed, both in terms of effect and cost on the person using them. Because this novel fills out the Universe of the Elemental Masters, I found it one of the best I've read recently.
Try this book, and go on to read the rest of the series if you haven't already. You'll be more than amply repaid for the effort.